// 동아리 홍보하기

#include <cstdio>
#include <algorithm>
#include <iostream>
#include <cstring>
#include <unordered_map>
#include <unordered_set>
#include <fstream>
#include <cmath>
#include <ctime>
#include <vector>
#include <stack>
#include <queue>
#include <functional>
#include <list>
#include <deque>
#include <numeric>
#include <set>
#include <climits>
#include <utility>
#include <map>
#include <float.h>
typedef long long ll;
typedef unsigned long long ull;
inline int max( int x, int y ){ return x > y ? x : y ; }
inline int min( int x, int y ){ return x < y ? x : y ; }
inline ll max( ll x, ll y ){ return x > y ? x : y ; }
inline ll min( ll x, ll y ){ return x < y ? x : y ; }
inline ull max( ull x, ull y ){ return x > y ? x : y ; }
inline ull min( ull x, ull y ){ return x < y ? x : y ; }
ll GCD( ll a, ll b ) { return b ? GCD( b , a%b ) : a; }
using namespace std;
#define INF 1000000000
#define MOD 1000000007
#define PIV 3.14159265358979323846
#define MAXN 200000
typedef pair<int, int> P;
const int MAX_V = 200000;

int G, H;
vector<int> adj[MAXN];
vector<bool> visited;
const int UNWATCHED = 0;
const int WATCHED = 1;
const int INSTALLED = 2;
int installed;

int DFS( int here ){
	visited[here] = true;
	int child[3] = { 0, 0, 0 };
	for( int i=0; i<adj[here].size(); ++i ){
		int there = adj[here][i];
		if( !visited[there] ) ++child[DFS(there)];
	}

	if( child[UNWATCHED] ){
		installed++;
		return INSTALLED;
	}

	if( child[INSTALLED] ) return WATCHED;
	return UNWATCHED;
}

int Camera(){
	installed = 0;
	visited = vector<bool>(G, false);
	for( int i=0; i<G; ++i ){
		if( !visited[i] && DFS(i) == UNWATCHED ){
			++installed;
		}
	}
	return installed;
}

int main(){

	int A, B;
	scanf("%d %d", &G, &H);
	for( int i=0; i<H; ++i ){
		scanf("%d %d", &A, &B);
		A--; B--;
		adj[A].push_back( B );
		adj[B].push_back( A );
	}
	printf("%d\n", Camera());
	return 0;
}